SparseMultiplyAdd(_:_:_:)
Performs the multiply operation y += Ax on a vector of double-precision, floating-point values.
Declaration
func SparseMultiplyAdd(_ A: SparseMatrix_Float, _ x: DenseVector_Float, _ y: DenseVector_Float)Parameters
- A:
The sparse matrix A in y += Ax.
- x:
The dense vector x in y += Ax.
- y:
The dense vector y in y += Ax.
Discussion
Use this function to multiply a sparse matrix by a dense vector and accumulate the result. The following equation is an example of a matrix-vector multiplication where the matrix is sparse:
[Image]
Call SparseMultiplyAdd(_:_:_:) to calculate the result.
let rowCount = Int32(4)
let columnCount = Int32(4)
let blockCount = 4
let blockSize = UInt8(1)
let rowIndices: [Int32] = [0, 3, 0, 3]
let columnIndices: [Int32] = [0, 0, 3, 3]
let data: [Float] = [1.0, 4.0, 13.0, 16.0]
/// The _A_ in _y+=Ax_.
let A = SparseConvertFromCoordinate(rowCount, columnCount,
blockCount, blockSize,
SparseAttributes_t(),
rowIndices, columnIndices,
data)
defer {
SparseCleanup(A)
}
/// The values for _x_ in _y+=Ax_.
var xValues: [Float] = [10.0, -1.0, -1.0, 10.0]
var yValues: [Float] = [1.0, 1.0, 1.0, 1.0]
/// The values for _y_ in _y+=Ax_.
yValues.withUnsafeMutableBufferPointer { yValuesPtr in
xValues.withUnsafeMutableBufferPointer { xValuesPtr in
/// The _x_ in _y+=Ax_.
let x = DenseVector_Float(count: 4,
data: xValuesPtr.baseAddress!)
/// The _y_ in _y+=Ax_.
let y = DenseVector_Float(count: 4,
data: yValuesPtr.baseAddress!)
SparseMultiplyAdd(A, x, y)
}
}
/// On return, `yValues` contains:
/// `[ 141.0, 1.0, 1.0, 201.0 ]`